Well, you didn't specify singles majors, so if you can create the ultimate singles AND doubles player, they will win 3 majors per major tournament considering they win the singles, doubles, and mixed doubles. So..... 3*4=12
100/12=8.33, so, they can win 100 majors in less than 9 years. But whoever does it better end up in the hall of fame.

Well, you didn't specify singles majors, so if you can create the ultimate singles AND doubles player, they will win 3 majors per major tournament considering they win the singles, doubles, and mixed doubles. So..... 3*4=12
100/12=8.33, so, they can win 100 majors in less than 9 years. But whoever does it better end up in the hall of fame.

But here's the reality: Jesus Christ Himself, if he came back and decided to take up tennis, couldn't win 100 grand slams within the human lifetime (alrighty, maybe he could, but I'm making a point).

On the other hand, 25 grand slams isn't as ridiculous as it sounds. If you read history books on tennis, you'll know that in many ways, guys like Laver could have been considered to have actually "won" (or easily had the ability to win) many more Grand Slams had they not been prevented from competing. I believe Moose Maloney informed me of this, in one particularly informative post of his.

I think that if nadal could get frozen cryogenically, and come back 100 years in the future, he would win teh grand slam many times. This is possible if all the surfaces continued to be slowed down to red clay eventually. That is of coarse, if andre agassi and stefi grafs son has a grandchild with some other super-talented female player.